1. Field of the Invention
The present invention relates to liquid filling systems and, more particularly, to the overall production rates (i.e. number of filled containers per minute per filling station) achieved by liquid filling systems utilizing either diverter valve technology or continuous-motion (e.g. walking beam) filling processes, and to the clean up (e.g. clean-out-of-place, clean-in-place) and calibration and/or set-up processes associated with their usage in a production environment.
2. Description of the Background
The production capability (e.g. containers per minute, containers per hour) of an automated filling system is a function of several factors. It is directly proportional to (1) the efficiency and number of filling stations that it possesses, (2) the technique used for indexing the containers to and from the filling stations, (3) the manner in which the filling nozzles move during the filling process, and (4) all system “downtime” associated with the clean up and calibration/set-up processes required for normal usage. While the number of filling stations in a given filling system can generally be varied within a certain range, the container indexing technique and the manner of filling nozzle motion are typically fixed aspects of an automated filling system's design possessing little, if any, operational adjustment.
The production capability of a semi-automated filling system is directly proportional to the efficiency and number of filling stations that it possesses, and the skill of the operator responsible for moving the containers to and from those filling stations. The overall production capability of either type of system, automatic or semi-automatic, is compromised by the amount of “downtime” required for cleaning, calibration/set-up, and periodic maintenance.
With respect to factor (1) above, each filling station typically includes a continuous-flow liquid metering device (e.g. rotary gear pump, rotary lobe pump, peristaltic pump, diaphragm pump, double-ended piston pump, flow meter, time/pressure filling head), a flexible intake/discharge tubing, and a filling nozzle. Conventional automated filling systems, equipped with any existing continuous-flow metering devices and possessing a one-to-one relationship between metering devices and filling nozzles, utilize only 45% to 60% of the maximum output volume, or total available dispensing time, of the metering device. Exactly where a filling system rates within the 45%-60% range is dependent upon factors such as (a) the type of indexing mechanism that controls the containers during the filling process; (b) the number of filling stations present, and/or (c) whether or not the nozzles move during the filling process.
Systems employing intermittent-motion indexing mechanisms tend toward the 45% rate of the aforementioned range because they must bring the empty containers to a stop before the filling process begins. Once the filling process is complete, the filled containers are allowed to resume movement in order to clear the filling area for the next set of empty containers. The liquid metering devices sit idle during the entire container indexing process and for part of the time that the nozzles are in motion. In contrast, systems employing continuous-motion indexing mechanisms tend toward the 60% end of the range because the containers are filled as they move through the filling area by a set of nozzles that travel in unison with them. While this is a more efficient process due to the simple fact that the containers are not brought to a stop during the filling cycle, there is still a significant portion of the output volume of the metering device that remains unused (i.e. the metering devices sit idle while the nozzles return to the infeed end of the filling area for the start of the next filling cycle).
It would, therefore, be greatly advantageous to provide automated, production environment liquid filling systems designed to utilize a greater percentage (i.e. approaching, or equal to 100%) of the maximum output volume, or total available dispensing time, of the metering devices.
There are also semi-automated production environment filling systems in which the filling and container handling processes are mutually exclusive steps in the overall machine cycle. The metering device sits idle while an operator removes the containers that have just been filled and replaces them with empty containers. After restarting the filling process, the operator then waits for that step to be completed before repeating the container removal/replacement process. It would, therefore, also be advantageous to provide a semi-automatic production environment liquid filling systems that likewise possess the means to increase production rate efficiencies by allowing the filling and container handling processes to occur simultaneously.
As the number of filling stations increases in either the automated or semi-automated systems described above, additional design goals and challenges arise. For instance, the cost of spare or replacement parts should be kept to a minimum, as should the amount of time required to changeover and/or clean out the system when changing from one liquid product to another. In general, a significant amount of “downtime” is required to clean filling machinery when changing from one product to another (see the detailed discussion of cleaning processes below). Therefore, a filling system providing an increase in overall production rate efficiency (i.e. filled containers per minute per pump) while requiring little or no increase in the amount of clean up/changeover downtime would be most desirable.
With respect to factors (2) and (3) above, systems employing intermittent-motion indexing mechanisms bring the empty containers to a stop before the filling process begins. Once the filling process is complete, the filled containers are allowed to resume movement in order to clear the filling area for the next set of empty containers. In systems employing continuous-motion indexing mechanisms, the containers are filled as they move through the filling area by a set of nozzles that travel in unison with them. It is readily apparent to those with ordinary skill in the art that a continuous-motion filling/indexing process, as compared to intermittent-motion indexing, is more efficient due to the simple fact that the containers are not brought to a stop during the filling process.
With respect to continuous-motion indexing systems, there are generally two techniques employed for moving the nozzles during the filling process. As seen in the prior art, in-line “walking beam” filling system 20 of FIGS. 1A and 1B, empty containers 21 moving in a straight line along a single-lane conveyor 22 (as indicated by directional arrow 24) are filled by a bank of nozzles 23 that travel in unison with them through the filling zone 26. Once the filling process is complete, the bank of nozzles 23 returns (as indicated by directional arrow 25) to the infeed end of the filling zone 26 to align itself with the next set of empty containers 21. In this fashion, every container 21 is filled as it moves through the filling zone 26.
Techniques similar to that described above have been utilized in a variety of in-line continuous-motion filling systems. For example, U.S. Pat. No. 5,971,041 to Drewitz discloses a machine for filling fluid products into containers delivered in a row by a conveyor that has a filling station with a walking nozzle bank (i.e. walking beam mechanism). The nozzle bank includes elongated gripper plates that are moved laterally to engage the containers while the nozzles are inserted therein. Once a batch of containers has been received in the filling station and engaged by the gripper plates, the container batch is allowed to move in the conveying direction together with the nozzle bank as the containers are being filled.
Another example is U.S. Pat. No. 4,004,620 to Rosen which discloses a filling machine for simultaneously filling several containers with a predetermined amount of fluid per container. The containers are indexed by a feed screw that moves the containers into the area of the machine where the nozzles are lowered into the containers to carry out the discharge of the fluid into the containers. The nozzle support structure is actuated to reciprocate in the direction of the movement of the containers while the containers are being filled and opposite this direction after the nozzles are raised to clear the tops of the containers.
Yet another example is U.S. Pat. No. 4,394,876 to Brown which discloses a filling machine for filling containers as they advance along a conveyor. Valved dispenser assemblies are moved in an upright closed loop course above the conveyor. They move in the direction of advance of the conveyor during the lower half of the closed loop course and in the opposite direction during the upper half of the closed loop course. Fluid pressure operated valve actuators are provided for operating the valves on the dispensers between their open and closed positions. A control mechanism is provided to control application of fluid pressure to the valve actuators in timed relation to the movement of the dispenser assemblies in their closed loop course.
The second technique for moving the nozzles during the filling process is shown the “rotary” indexing system 40 of FIG. 2 where the nozzles 41 and corresponding containers (not shown in FIG. 2) travel in a circular path through the filling zone 44 (as indicated by directional arrow 46). While a system 40 of this type is generally recognized as being more complex and costly than an in-line walking beam system, it does possess the ability to achieve higher overall production rates. An empty container is transferred from the conveyor 42 to a position under a nozzle 41 by the infeed turret 43 and is filled as the container/nozzle 41 combination travels through the filling zone 44. The filling process is completed by the time the container reaches the discharge turret 45 where the filled container is removed from beneath the nozzle 41 and returned to the conveyor 42.
Unfortunately, both of the prior art continuous-motion filling processes described above possess certain shortcomings. In-line, walking beam systems utilizing single-lane conveyors possess overall production rate limitations that are practical functions of the physical size of the walking beam assembly and the length/distance of its travel during the filling process. The maximum length/distance of travel is equal to approximately two-thirds of the length of the walking beam assembly's nozzle mounting bracket, or in other words, the length of the set of containers that are to be filled during each filling cycle. This limitation is imposed by the need for the bank of nozzles to return to the infeed end of the filling zone in order to begin filling the next set of empty containers, and results in maximum overall production rate capabilities that fall far short of those possible with rotary filling systems.
On the other hand, rotary systems are generally more complex in design and construction than in-line walking beam systems. For example, the filling stations (i.e. metering devices such as lobe pumps or flow meters, any associated metering device drive mechanisms, filling nozzles, rigid or flexible intake/discharge tubing, product feed components such as a tank or manifold) must rotate in conjunction with the movement of the containers. Conversely, in a walking beam system, only the nozzles and discharge tubing travel with the containers, the other filling station components typically remain stationary. In addition, the changeover process between production runs associated with a rotary system is more time consuming and costly in terms of both actual and opportunity costs.
It would, therefore, be greatly advantageous to provide automated liquid filling systems possessing production rate capabilities approaching, or equal to, those of “rotary” filling systems while retaining the relative simplicity of design and changeover inherent in in-line “walking beam” systems equipped with single-lane conveyors.
With respect to factor (4) above, the filling of liquids in a production environment involves a significant amount of “downtime” for the cleaning of the machinery (product contact parts) when changing from one product (or batch) to another. The cleaning process, while known to be of a time consuming nature, is acknowledged as a “necessary evil” in order to avoid potentially hazardous problems with cross-contamination between products/batches. There are three methods typically employed to complete a cleaning cycle for the product contact parts.
The first is a process that subjects the product contact parts to a cleaning cycle without removing them from the production environment (known as “clean-in-place” or CIP). This process typically utilizes a separate cleaning system that is the combination of cleaning fluid reservoirs, a fluid circulating pump, and a sophisticated control scheme. The primary detriment associated with the use of a CIP process is the “opportunity cost” associated with not being able to operate the filling system in its production mode while the product contact parts are being subjected to the cleaning cycle.
The second cleaning method requires the removal of the product contact parts from the production environment. The most efficient utilization of this method requires a second complete set of “clean” product contact parts (for use in the production environment while the first set is cleaned) and one or more individuals to manually disassemble, clean, and reassemble the “dirty” set of product contact parts. The disassembly/cleaning/re-assembly process is labor intensive and subjects the individuals involved to potentially hazardous products, cleaning fluids, or the combinations thereof.
The third method utilizes two, separate and complete filling systems positioned in series in the production environment. While one system is subjected to the cleaning cycle, the second is used for a production run. However, there are very few situations where the combination of cost and floor space required by two, separate and complete filling systems makes for a profitable production environment.
In today's business environment of minimal inventories and “just in time” manufacturing, it is simply not economically feasible to dedicate an entire liquid filling system to a single product. It would, therefore, be greatly advantageous to supply a cost effective and space efficient liquid filling system possessing the ability to be rapidly changed over from one product (or batch) to another while still providing the opportunity to thoroughly clean all of the product contact parts in order to avoid cross-contamination issues. Furthermore, the system should not require a time-consuming disassembly/cleaning/re-assembly process for any of the product contact parts nor cause employees to be exposed to hazardous materials.
Again with respect to factor (4) above, the calibration and/or set-up of the metering devices (i.e. pumps) in a production environment liquid filling system can also be a time consuming, labor intensive process. However, it is acknowledged to be another “necessary evil” in order to maximize the effectiveness (i.e. fill accuracy, average production rate) of the subsequent production run. A number of steps are typically included in the calibration/set-up process for a liquid filling system.
The first step is the priming of the metering devices. The intake line leading from the product supply vessel to each metering device, the metering device itself, and the discharge line running from each metering device to each dispensing nozzle must be filled with the product. To maximize the fill accuracy of the liquid filling system, the priming process must also purge all air from the metering devices, nozzles, and intake/discharge lines. This is typically accomplished by moving the dispensing nozzles from their normal operating position over the container handling/indexing system to a position that places them above a product collection receptacle. The moving of the nozzles in this manner is a manual process. The amount of time required to reposition the nozzles is directly proportional to the number included in the liquid filling system.
Once the nozzles are in position above the collection receptacle, the metering devices are actuated by the operator in order to draw the product from the supply vessel into the intake lines and, after passing through the metering devices, out through the discharge lines. This is typically done using a cycle rate that is effective in purging any entrapped air. Metering devices that are not self-priming in this manner require either a positive pressure product supply vessel or a gravity-assisted product feed from an elevated supply tank. The product used for the priming process (i.e. present in the collection receptacle at the end of the process) may, or may not, depending on the nature of the product and/or the regulations under which it is manufactured, be reclaimed and recycled back into the main product supply tank.
After the priming process is complete, each metering device must be calibrated to dispense the proper amount of product during each filling cycle. This is generally accomplished in one of two ways. The first method requires each metering device to be completely calibrated (i.e. gross and fine adjustments) individually in a sequential manner. The second involves the process of making a global (i.e. all metering devices simultaneously) gross fill volume adjustment before fine tuning each metering device individually in a sequential manner. The choice between the two methods typically hinges on the total number of metering devices included in the liquid filling system. As the number of metering devices increases, the efficiency and effectiveness of the second method also increases.
Both methods require an operator to enter into the control system a gross adjustment set point corresponding to the desired fill volume. This is typically a number calculated to estimate the number of metering device cycles/revolutions required to displace the desired amount of liquid (e.g. desired fill volume divided by volume per metering device cycle or revolution). The first method requires that set point to be entered for each of the metering devices; the second allows a single entry to be forwarded to all of the metering devices.
Once the gross adjustment set points have been established, each metering device typically must be individually fine tuned (i.e. it is rare that the gross adjustment provides the desired fill volume within the required degree of accuracy). The fine tuning process generally involves actuating a metering device dispense cycle, collecting the product dispensed in a tare-weighed container, and weighing the filled container to obtain the net weight of the product included therein. If the net weight of the dispensed product is not within the required degree of accuracy, a minor upward or downward manual adjustment of the set point is entered into the control system before repeating the process. This process is repeated until the product dispensed by the metering device falls within the required degree of fill volume accuracy.
In order to ensure that a production run remains within specifications (e.g. fill volume accuracy), periodic fill weight verification is generally performed. This process is typically accomplished manually by (1) introducing a number of tare-weighed containers (i.e. equal to the number of metering devices/dispensing nozzles) into the stream of empty containers entering the liquid filling system, collecting the containers after they have been filled, and calculating the net weight of the product therein, or (2), in a sequential manner involving all of the metering devices, catching the product dispensed by each of them in a tare-weighed receptacle in order to determine the net weight of the filling cycle output. If any of the metering devices are found to be dispensing too much, or too little, the operation of the liquid filling system is typically suspended temporarily to allow an operator to restore a proper fill volume set point using a process similar to the fine tuning procedure discussed above.
In any of the manual processes discussed above, the possibility of operator error exists. Examples of potential operator error include (1) the failure to properly position a nozzle over the collection receptacle during the priming/air purging process, (2) the entering of an incorrect gross adjustment set point at the start of the filling cycle calibration process, (3) making an incorrect association between a net fill weight and the fill station that generated it (and subsequent fine tuning adjustment of the wrong fill station) during either the filling cycle calibration or the fill weight verification process, and (4) the misreading or miscalculation of otherwise correct fill weights leading to unnecessary fine tuning adjustments during either the filling cycle calibration or the fill weight verification process.
In addition to the actual costs, outlined above in terms of manual labor and product waste (e.g. inaccurate fills resulting from air in the intake or discharge lines, the iterative process used to establish proper fill volumes, operator error), the calibration/set-up process also carries the “opportunity cost” associated with not being able to operate the liquid filling system in its production mode while the calibration/set-up process is ongoing. Obviously, the more time required to complete a manual calibration/set-up process, the greater the associated opportunity cost. It would, therefore, be greatly advantageous to supply a cost effective, time efficient, automated means to calibrate/set-up the metering devices in a production environment liquid filling system.